Field of the Invention
The present invention relates to a light source unit and an image projection system including this light source unit.
Description of the Related Art
In these days, data projectors are used on many occasions as an image projection system which projects an image of a screen of a personal computer or a video image, as well as images based on image data which is stored on a memory card or the like on to a screen. Conventionally, the mainstream of these projectors has been those which utilize a high-intensity discharge lamp as a light source. In recent years, however, there have been made many developments and proposals on light source units which use, as light emitting elements, light emitting diodes (LEDs), laser light emitting devices, organic electroluminescent devices or luminescent materials.
The Japanese Unexamined Patent Application No. 2012-123967 discloses an image projection system. In this image projection system, a laser light emitting device is used as a light source which emits a laser beam part of which is used as excitation light to illuminate a luminescent material to thereby cause it to emit luminescent light. Then, light source light for forming bright image is generated by combination of the laser beam and the luminescent light, enabling the emission of highly bright image forming light. Further, various types of similar image projection systems have been proposed, some of which are now provided for sale on the market.
With such a light source unit which uses a semiconductor light emitting device such as a laser light emitting device or the like and a luminescent light emitting plate on which a luminescent material is provided, it is easy to form bright three primary colors of light, enabling the projection of a bright color image. However, the high-intensity light source tends to have a high heating value, and as a result of that, it has been difficult to use it in order to make up a light source unit which is small in size and which has high cooling and heat dissipating effects.
Additionally, in the event that lenses and mirrors get dirty with time, although it is small, there is a possibility that the brightness of an image produced is deteriorated. As this occurs, not only is the brightness of the image deteriorated, but also a reduction in tone or clarity of a projected image is caused. Further, the heating value in the optical system is increased. Thus, light sources of this type have caused various problems including those described above.